1. Field of the Invention
The present invention relates to a loudspeaker suspension device and a fabricating method thereof, and more particularly to a loudspeaker suspension device and a fabricating method thereof, capable of providing an improved connection state of signal input ends of voice coil connection conductors.
2. Related Background Art
In order to reduce the number of wiring steps of a loudspeaker, various types of dampers with conductors 2 (hereinafter called "conductive damper ID) have been proposed heretofore, in which the conductors 2 are provided along corrugations 11c of a suspension 1 generally called spiders or dampers. However, these conductive dampers 1D are not satisfactory in terms of practical use. As described in EP 0 369 434 A2 and EP 0 479 317 A2, the inventors have proposed practically usable conductive dampers (hereinafter called "sewn conductive dampers 1Ds) which are already under mass production. This sewn conductive damper uses as the conductors 2 conductive wires (hereinafter called "flat knitted tinsel wires 2h) made of a desired number of flat knitted conductive wires each formed by winding a copper foil around fibers. This flat knitted tinsel wire is sewn on a base cloth B made of woven cloth and constituting a suspension 1. The base cloth B with the sewn flat knitted tinsel wires is thermally molded to attache the conductors 2 along corrugations 11c. An edge (hereinafter called a "conductive edge 1E") utilizing the technology proposed by the inventors has also been proposed.
A loudspeaker suspension 1 such as a sewn conductive damper 1Ds and a conductive edge 1E, having conductor 2 along corrugations 11c or roll 11r of the suspension 1, is called a "conductive suspension 1".
The structure of the conductive suspension 1 having the conductors 2 mounted along the corrugations 11c or roll 11r of a conventional general loudspeaker suspension will be described by taking as an example the conductive damper 1D and the conductive edge 1E. In manufacturing the conductive damper 1D, for example, in manufacturing the sewn conductive damper 1Ds proposed by the present inventors, phenol resin raw liquid generally sold in markets is diluted with methanol to obtain phenol resin solution having a desired specific gravity. Woven cloth made of cotton or chemical fibers is dipped in this solution to impregnate or coat it with the phenol resin. After the methanol solvent is evaporated to remove resin tucking, the woven cloth is cut to have a predetermined width. In this manner, the base cloth B used for damper molding is prepared.
Two flat knitted tinsel wires 2h as the conductors 2 are sewn to the base cloth B with sewing threads 3 called cornex, in parallel along the center line and at a predetermined space relative to the center line, as shown in FIG. 8. After the flat knitted tinsel wires 2h are sewn, the base cloth B is thermally pressed, similar to general dampers, to integrally mold the corrugations 11c concentrically to the center line of the base cloth B, as shown in FIG. 9. Thereafter, unnecessary portions indicated by broken lines in FIG. 10 are trimmed through punching press. In this manner the sewn conductive damper 1D with the flat knitted tinsel wires 2h being mounted along the corrugations 11c can be obtained as shown in FIGS. 11A and 11B.
The manufacture of the conductive edge 1E, for example, the sewn conductive edge 1Es (refer to FIG. 3 of an embodiment of the invention) the present inventors have proposed in practical use, is basically the same as the manufacture of the sewn conductive damper 1Ds. Specifically, a predetermined woven cloth is impregnated with phenol resin or the like having a predetermined concentration and coated with a predetermined damping material such as synthetic rubber to prepare the edge material. This edge material is cut to have a predetermined width to prepare the base cloth B to be used for edge molding. Two flat knitted tinsel wires 2h similar to the above-described wires 2h as the conductors 2 are sewn to the base cloth B with sewing threads 3 called cornex, in parallel along the center line and at a predetermined space relative to the center line.
After the flat knitted tinsel wires 2h are sewn, the base cloth B is thermally pressed, similar to general edge molding, to integrally mold the roll 11r relative to the center line of the base cloth B. Thereafter, unnecessary portions are trimmed. Generally, if the unnecessary portions are cut through punching press, the sewn conductive edge 1Es with the flat knitted tinsel wires 2h being mounted along the roll 11r can be obtained.
The structure of the conductive suspension 1 of a conventional loudspeaker is fabricated in the above method. It is therefore obvious that the conductor 2 made of the flat knitted tinsel wire 2h is disposed on the front surface of the suspension base cloth B made of a woven cloth impregnated or coated with resin. Therefore, exposed is only one side of the conductor 2, i.e., the flat knitted tinsel wire 2h, and the other side is hidden in contact with the suspension base cloth B.
Next, a means for electrically interconnecting the conductor 2 and an input terminal lug 4 will be described by taking as an example the sewn conductive damper 1Ds. As shown in FIGS. 11A and 11B, tongue-shaped projections (hereinafter called tongue portions 13a and 13b) are provided extending outward from an adhesion portion 12 at the circumferential area of the sewn conductive damper where the conductors 2 or sewn flat knitted tinsel wires 2h reach. The ends 2ha and 2hb of the flat knitted tinsel wires 2h extend on the tongue portions 13a and 13b.
In order to perform electrical connection under the conditions that the sewn conductive damper 1Ds is mounted on a speaker frame F, as shown in FIG. 12, the tongue portions 13a and 13b are disposed on input terminals mounted on the speaker frame F. The surfaces of the ends 2ha and 2hb of the flat knitted tinsel wires 2h at the tongue portions 13a and 13b are made in contact with, or pressed against, partial areas of terminal lugs 4a and 4b, and the contact areas or pressed areas of the lugs 4a and 4b are soldered. Therefore, partial areas of the terminal lugs 4a and 4b are made always in contact with the front surfaces of the conductors 2 (flat knitted tinsel wire ends 2ha and 2hb).
Another approach is to separate the ends of conductors 2 or flat knitted tinsel wire ends of the sewn conductive damper 1Ds from the damper base cloth B to expose both the front and back surfaces of the flat knitted tinsel wire ends 2ha and 2hb and jump the ends 2ha and 2hb directly to the input terminal lugs 4. This connection structure of the sewn conductive damper 1Ds has been proposed by the present inventors, as described in Japanese Patent Laid-Open Gazette No. HEI 2-134100 and Utility Model Laid-Open Gazette No. HEI 2-13398.
In this electrical connection process, as shown in FIGS. 13A and 13B, the tongue portions 13a and 13b at the damper circumferential area are required to be separated from the flat knitted tinsel wire ends 2ha and 2hb on the tongue portions 13a and 13b, by loosening the sewing thread 3 in the range from the outermost ends of the tongue portions 13a and 13b to the outermost circumference of the adhesive area 12. It is also necessary to peel off the flat knitted tinsel wire ends 2ha and 2hb from the tongue portions 13a and 13b to cut the loosened threads 3. Thereafter, both the front and back surfaces of the flat knitted tinsel wire ends 2ha and 2hb are exposed to separate them from the damper base cloth B (tongue portions 13a and 13b). This process, however, has the problems of (1) high cost and (2) unstable product quality.
The reason of the high cost (1) is as follows. The process of loosening the sewing threads 3 is very complicated and the number of works increases, resulting in the high cost. The unstable product quality (2) results from a variation in the works of loosening the sewing threads 3. If the thread 3 is loosened too much, it is loosened even near to the ends of the corrugations 11c, and the unfastened portion is formed at the outermost circumference of the corrugations 11c.
In operation of the sewn conductive damper 1Ds having the unfastened portion near at the corrugations 11c, since the corrugations 11s are movable, they vibrate and the flat knitted tinsel wires 2h near at the corrugations contact with the damper base cloth B to generate abnormal sounds called vibratory sounds. If such a state continues for a long time, the copper foils constituting the flat knitted tinsel wires 2h at the unfastened portion are cut, resulting in a fatal defect of no sound from the loudspeaker.
Even if the portion where the sewing thread 3 is loosened does not reach the outermost circumference of the corrugations 11c, the end of the sewing thread 3 may be loosened by vibrations or impacts during the transportation of the damper, and this loosened portion may often reach the outermost circumference of the corrugations 11c. From the reasons described above, an approach to separating the conductors 2 (flat knitted tinsel wires 2h) of the sewn conductive damper 1Ds from the damper base cloth B (tongue portions 13a and 13b) is not still realized to date.
There are some advantageous cases, however, if the conductors 2 are separated from the damper base cloth B, i.e., if both the front and back sides of the ends 2ha and 2hb of the flat knitted tinsel wires 2h are exposed not to intentionally mount the conductors 2 on the woven cloth (at the tongue portions 13a and 13b or the like) of the base cloth B of the sewn conductive damper 1Ds. For example, such a case occurs if the conductive damper 1D is used with a terminal ring L or the like provided with wiring patterns the present inventors have proposed.
Specifically, in the case of the sewn conductive damper 1Da (FIG. 12) with the conductors reaching the tongue portions 13a and 13b, the woven cloth (at the tongue portions 13a and 13b or the like) of the suspension base cloth B is interposed at a contact surface between the ends 2ha and 2hb of the flat knitted tinsel wires 2h and the wiring conductive patterns (FIG. 14). Therefore, electrical connection by soldering is almost impossible. In order to allow soldering, the present inventors have proposed specific conductive dampers 1D which we call a woven conductive damper 1Di.
More in detail, a terminal ring L formed through punching press of a printed circuit board or the like made of a resin board attached with copper foils or the like, is integrally formed with three projections L1, L2 and L3 separated by 90.degree. about the ring center, as shown in FIG. 14. The projection L1 is formed at the position where terminals are mounted, and the other two projections L2 and L3 are formed at the positions separated by 180.degree. about the ring center. A wiring pattern P is also formed on the side where the conductive damper 1D is mounted. Square holes L11 for mounting terminal lugs 4 are formed as shown in FIG. 14 in the tongue-shaped projection L1 on which the input terminals are connected. Caulking portions 41 of the terminal lugs 4 are inserted into the holes L11 and caulked to press a partial area of each terminal lug 4 against the surface of the wiring pattern P to thus complete the ring L with the terminal lugs 4.
In manufacturing the damper, fibers constituting the base cloth B is impregnated with phenol resin having a predetermined concentration and diluted with methanol, and the solvent is evaporated to remove resin tucking. Fibers impregnated with the resin are used as warps and fibers not impregnated with the resin are used as yarns, and one flat knitted tinsel wire 2h is woven on the side of yarns. The base woven cloth B with the flat knitted tinsel wire 2h disposed on the center line of the damper corrugations 11c is thermally molded to obtain the woven conductive damper 1Di.
Since a damper inner diameter portion 13 (FIG. 11) is cut by a trimming process, the flat knitted tinsel wire 2h disposed on the damper center line is cut so that two flat knitted tinsel wires 2h are disposed along the damper center line. At the trimming process, two tongue portions 13a and 13b are formed outside of the adhesion portion 12 at the damper circumferential area, as shown in FIG. 14, so that the flat knitted tinsel wire ends 2ha and 2hb reach the tongue portions 13a and 13b. Since the woven conductive damper 1Di has the structure that the flat knitted tinsel wire 2h is woven in the woven cloth, the copper foils of the flat knitted tinsel wire 2h as the conductor 2 are exposed between fibers constituting the woven cloth (between weaving spaces).
As shown in FIG. 14, a predetermined amount of rubber-containing adhesion h is coated on the inner peripheral area of the terminal ring L, and the terminal ring L is dried for a predetermined time to evaporate the solvent of the adhesive h. Cream solder sc (FIG. 15) is coated on a predetermined area of the pattern P on the projections L2 and L3, i.e., on the area where the ends of the flat knitted tinsel wires 2h of the woven conductive wire 1Di reach. The damper adhesion portion 12 and the outer circumferential portion of the ring L with the terminals are aligned in position, and the damper tongue portions 13a and 13b and the ring projections L2 and L3 are aligned in position. Therefore, the adhesive portion 12 of the woven conductive damper 1Di and the area with the adhesive h are made in contact with each other, and the cream solder sc and the exposed areas of the back surface of the flat knitted tinsel wires reaching the projections of the woven conductive damper 1Di are made in contact with each other.
In this state, thermal press is applied for several seconds at about 250.degree. C. down to the adhesion portion 12 and tongue portions 13a and 13b of the damper 1Di to thermally reactivate the adhesive h. While the adhesion portion 12 of the woven conductive damper 1Di is attached to the terminal ring L and the cream solder sc is melted, the exposed areas of the back surfaces of the flat knitted tinsel wire ends 2ha and 2hb reaching the tongue portions 13a and 13b of the woven conductive damper 1Di are soldered to the wiring patterns P of the ring L. In this manner, the woven conductive damper 1Di with the ring L and the terminal lugs 4 can be formed (refer to FIG. 15).
During the thermal press, phenol resin or the like will not be attached to the flat knitted tinsel wires 2h as the conductors 2 of the woven conductive damper 1Di. Furthermore, the copper foils constituting the flat knitted tinsel wires 2h are exposed between weaving spaces of the base woven cloth B and the exposed areas are made in contact with the wiring conductive patterns P of the ring L. Therefore, it is easy to solder. However, a general sewn conductive damper 1Ds with the tongue portions 13a and 13b reaching the conductors 2 (flat knitted tinsel wire ends 2ha and 2hb) is difficult to use with such a structure described above. The types of conductive dampers ID are therefore limited and the use range of the ring L with the wiring conductive patterns P is narrowed.
In order to solve this problem, it is necessary that copper foils of the conductors 2 or flat knitted tinsel wire ends 2ha and 2hb are intentionally disposed to be separated from the base woven cloth B of the sewn conductive damper 1Da. In order to separate the flat knitted tinsel wire ends 2ha and 2hb reaching the tongue portions 13a and 13b, as described previously, the sewing threads 3 were loosened to peel off the flat knitted tinsel wires 2h from the tongue portions 13a and 13b, and the tongue portions 13a and 13b and the loosened threads 3 were cut. However, although the problem (1) of the increased works may be absorbed in the total number of manufacture processes of a loudspeaker, the problem (2) causing a fatal defect could not be solved.
Specifically, the ends of the sewing thread of the sewn conductive damper 1Ds reaching the outer circumference of the adhesion portion 12 or the outermost end of the tongue portion are subjected to the thermal molding, under the conditions that the ends are in tight contact with the flat knitted tinsel wires 2h and damper base cloth B. Therefore, the ends are maintained in tight contact even after the molding. Furthermore, the sewing threads 3 on the base cloth B are in a semi-adhered state caused by phenol impregnated to the woven cloth. Therefore, the sewing threads 3 reaching the outermost area will not loosened unless a particular force is applied thereto.
However, if the tightly molded sewing threads 3 are once forcibly loosened, the tightly molded state or semi-adhered state of the sewing threads 3 is broken and the ends of the sewing threads 3 are loosened. In such a case, it has been found that if the separated or unfastened portion of the flat knitted tinsel wires 2h reaches near the middle portion of the adhesion portion 12 and if the sewing thread 3 was cut at the outer circumferential area of the adhesion portion 12, because of a variation in the loosening degree of the sewing threads 3, then many of the sewing threads 3 are loosened near to the outermost corrugation 11c by a very small external force, particularly by a very small external force applied to the flat knitted tinsel wire ends 2ha and 2hb during product transportation.
An example of an advantageous case will be described with reference to FIG. 16, the advantageous case being realized if the exposed areas of the conductors 2 or flat knitted tinsel wire ends 2ha and 2hb or the like of the conductive edge 1E are not mounted on the woven cloth B of the edge. For example, such a case occurs when the flat knitted tinsel wire ends 2ha and 2hb are required to be disposed on the back side of the edge 1E. In such a case, in order to electrically interconnect the flat knitted tinsel wire ends 2ha and 2hb to the input terminal lugs 4, the tongue portions 13a and 13b are provided as in conventional manner to dispose the flat knitted tinsel wire ends 2ha and 2hb on the input terminal lugs 4 for making them in contact with each other. In this state, however, as shown in FIG. 16, the edge base cloth B covers the whole surface of the terminal lugs 4 and the whole surface of the contact area between the flat knitted tinsel wire ends 2ha and 2hb and the terminal lugs 4.
Therefore, although it is easy to make the flat knitted tinsel wire ends 2ha and 2hb in contact with the terminal lugs 4, it is very difficult to maintain a state that the flat knitted tinsel wire ends 2ha and 2hb are pressed and fixed to the terminal lugs 4. Moreover, since the edge base cloth B having good electrical insulation covers the flat knitted tinsel wire ends 2ha and 2hb as shown in FIG. 16, it is difficult to achieve reliable soldering with the solder s and a soldering work itself is very difficult.
As a countermeasure for this, the flat knitted tinsel wire ends 2ha and 2hb reaching the tongue portions 13a and 13b made of the edge base cloth B may be separated to loosen the sewing threads 3 and peel off the flat knitted tinsel wire ends 2ha and 2hb from the tongue portions 13a and 13b to thereby cut the tongue portions 13a and 13b and not to interpose the base cloth B. Even in this state, similar to the above-described case, the sewing threads 3 are loosened to the roll portion 11r and the unfastened portion is formed to the roll portion 11r.
There is also another electrical connection approach. Specifically, the tongue portions 13a and 13b are provided at the areas where the flat knitted tinsel wire ends 2ha and 2hb outside of the adhesion portion 12 of the edge 1E reach, and the tongue portions 13a and 13b are bent to the front side whereas the back surface side of the flat knitted tinsel wire ends 2ha and 2hb reaching the tongue portions 13a and 13b is turned to the front side to expose it at the front side of the edge base cloth B, as shown in FIGS. 16A and 16B, to thereby press the exposed area against partial areas of the terminal lugs. This approach obviously requires an additional process of bending the tongue portions 13a and 13b, and the terminal lugs 4 are required to have a specific shape as shown.